In a variety of medical procedures, treatments, and research, it is desirable to provide repeated but intermittant drug delivery into the eye or into other spaces within the orbit of the eye. In the past such techniques have involved the implanting of osmotic mini-pumps attached to silastic tubing implanted in the eye, See, e.g., Miki, "A Method for Chronic Drug Infusion into the Eye", 28 Jap. J. of Ophthalmol., 140 (1984); Eliason, "An Ocular Perfusion System," 19 Invest. Ophtholmol. Vis. Sci. 102 (1980); Michelson, "Experimental Endophthalmitis Treated with an Implantable Osmotic Minipump," 97 Arch. Ophthalmol. 1345 (1979); and Miki, "Intraocular Cannula for Continuous, Chronic Drug Delivery," 103 Arch. Ophthalmol. 712 (1985).
All of these devices, however, require the implantation of a mini-pump which must be designed and prepared to deliver a specific predetermined drug desired. These devices are large and cumbersome to attach to the eye for even a few days. They give only a slow, constant infusion, being incapable of delivering a bolus, or of delivering selectively different drugs over an intermittant time period. Furthermore, such devices depend upon the presence of a pumping pressure to prevent reflux of fluid out of the cavity into which the drug is being infused. If the pump becomes detached, either purposely or accidentally, there is no mechanism to prevent extrusion of ocular fluids, causing loss of pressure in and damage to the eye.